 /*******************************************************************************
  * Copyright (c) 2000, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.ui.internal.handlers;

 import java.lang.reflect.InvocationTargetException ;
 import java.lang.reflect.Method ;

 import org.eclipse.core.commands.AbstractHandler;
 import org.eclipse.core.commands.ExecutionEvent;
 import org.eclipse.core.commands.ExecutionException;
 import org.eclipse.core.runtime.IConfigurationElement;
 import org.eclipse.core.runtime.IExecutableExtension;
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.widgets.Composite;
 import org.eclipse.swt.widgets.Control;
 import org.eclipse.swt.widgets.Display;
 import org.eclipse.ui.internal.ExceptionHandler;

 /**
  * Handles the cut command in both dialogs and windows. This handler is enabled
  * if the focus control supports the "cut" method.
  *
  * @since 3.0
  */
 public class WidgetMethodHandler extends AbstractHandler implements
         IExecutableExtension {

     /**
      * The parameters to pass to the method this handler invokes. This handler
      * always passes no parameters.
      */
     protected static final Class [] NO_PARAMETERS = new Class [0];

     /**
      * The name of the method to be invoked by this handler. This value should
      * never be <code>null</code>.
      */
     protected String methodName;

     public Object execute(final ExecutionEvent event) throws ExecutionException {
         final Method methodToExecute = getMethodToExecute();
         if (methodToExecute != null) {
             try {
                 final Control focusControl = Display.getCurrent()
                         .getFocusControl();
                 if ((focusControl instanceof Composite)
                         && ((((Composite) focusControl).getStyle() & SWT.EMBEDDED) != 0)) {
                     /*
                      * Okay. Have a seat. Relax a while. This is going to be a
                      * bumpy ride. If it is an embedded widget, then it *might*
                      * be a Swing widget. At the point where this handler is
                      * executing, the key event is already bound to be
                      * swallowed. If I don't do something, then the key will be
                      * gone for good. So, I will try to forward the event to the
                      * Swing widget. Unfortunately, we can't even count on the
                      * Swing libraries existing, so I need to use reflection
                      * everywhere. And, to top it off, I need to dispatch the
                      * event on the Swing event queue, which means that it will
                      * be carried out asynchronously to the SWT event queue.
                      */
                     try {
                         final Object focusComponent = getFocusComponent();
                         if (focusComponent != null) {
                             Runnable methodRunnable = new Runnable () {
                                 public void run() {
                                     try {
                                         methodToExecute.invoke(focusComponent,
                                                 null);
                                     } catch (final IllegalAccessException e) {
                                         // The method is protected, so do
 // nothing.
 } catch (final InvocationTargetException e) {
                                         /*
                                          * I would like to log this exception --
                                          * and possibly show a dialog to the
                                          * user -- but I have to go back to the
                                          * SWT event loop to do this. So, back
                                          * we go....
                                          */
                                         focusControl.getDisplay().asyncExec(
                                                 new Runnable () {
                                                     public void run() {
                                                         ExceptionHandler
                                                                 .getInstance()
                                                                 .handleException(
                                                                         new ExecutionException(
                                                                                 "An exception occurred while executing " //$NON-NLS-1$
 + methodToExecute
                                                                                                 .getName(),
                                                                                 e
                                                                                         .getTargetException()));
                                                     }
                                                 });
                                     }
                                 }
                             };

                             swingInvokeLater(methodRunnable);
                         }
                     } catch (final ClassNotFoundException e) {
                         // There is no Swing support, so do nothing.

                     } catch (final NoSuchMethodException e) {
                         // The API has changed, which seems amazingly unlikely.
 throw new Error ("Something is seriously wrong here"); //$NON-NLS-1$
 }

                 } else {

                     methodToExecute.invoke(focusControl, null);
                 }

             } catch (IllegalAccessException e) {
                 // The method is protected, so do nothing.

             } catch (InvocationTargetException e) {
                 throw new ExecutionException(
                         "An exception occurred while executing " //$NON-NLS-1$
 + methodToExecute.getName(), e
                                 .getTargetException());

             }
         }

         return null;
     }

     /**
      * Invoke a runnable on the swing EDT.
      *
      * @param methodRunnable
      * @throws ClassNotFoundException
      * @throws NoSuchMethodException
      * @throws IllegalAccessException
      * @throws InvocationTargetException
      */
     protected void swingInvokeLater(Runnable methodRunnable)
             throws ClassNotFoundException , NoSuchMethodException ,
             IllegalAccessException , InvocationTargetException {
         final Class swingUtilitiesClass = Class
                 .forName("javax.swing.SwingUtilities"); //$NON-NLS-1$
 final Method swingUtilitiesInvokeLaterMethod = swingUtilitiesClass
                 .getMethod("invokeLater", //$NON-NLS-1$
 new Class [] { Runnable .class });
         swingUtilitiesInvokeLaterMethod.invoke(
                 swingUtilitiesClass,
                 new Object [] { methodRunnable });
     }

     /**
      * Find the swing focus component, if it is available.
      *
      * @return Hopefully, the swing focus component, but it can return <code>null</code>.
      * @throws ClassNotFoundException
      * @throws NoSuchMethodException
      * @throws IllegalAccessException
      * @throws InvocationTargetException
      */
     protected Object getFocusComponent() throws ClassNotFoundException ,
             NoSuchMethodException , IllegalAccessException ,
             InvocationTargetException {
         final Class focusManagerClass = Class
                 .forName("javax.swing.FocusManager"); //$NON-NLS-1$
 final Method focusManagerGetCurrentManagerMethod = focusManagerClass
                 .getMethod("getCurrentManager", null); //$NON-NLS-1$
 final Object focusManager = focusManagerGetCurrentManagerMethod
                 .invoke(focusManagerClass, null);
         final Method focusManagerGetFocusOwner = focusManagerClass
                 .getMethod("getFocusOwner", null); //$NON-NLS-1$
 final Object focusComponent = focusManagerGetFocusOwner
                 .invoke(focusManager, null);
         return focusComponent;
     }

     public final boolean isEnabled() {
         return getMethodToExecute() != null;
     }

     /**
      * Looks up the method on the focus control.
      *
      * @return The method on the focus control; <code>null</code> if none.
      */
     protected Method getMethodToExecute() {
         final Control focusControl = Display.getCurrent().getFocusControl();
         Method method = null;

         if (focusControl != null) {
             final Class clazz = focusControl.getClass();
             try {
                 method = clazz.getMethod(methodName, NO_PARAMETERS);
             } catch (NoSuchMethodException e) {
                 // Fall through...
 }
         }

         if ((method == null)
                 && (focusControl instanceof Composite)
                 && ((((Composite) focusControl).getStyle() & SWT.EMBEDDED) != 0)) {
             /*
              * We couldn't find the appropriate method on the current focus
              * control. It is possible that the current focus control is an
              * embedded SWT composite, which could be containing some Swing
              * components. If this is the case, then we should try to pass
              * through to the underlying Swing component hierarchy. Insha'allah,
              * this will work.
              */
             try {
                 final Object focusComponent = getFocusComponent();
                 if (focusComponent != null) {
                     final Class clazz = focusComponent.getClass();

                     try {
                         method = clazz.getMethod(methodName, NO_PARAMETERS);
                     } catch (NoSuchMethodException e) {
                         // Do nothing.
 }
                 }
             } catch (final ClassNotFoundException e) {
                 // There is no Swing support, so do nothing.

             } catch (final NoSuchMethodException e) {
                 // The API has changed, which seems amazingly unlikely.
 throw new Error ("Something is seriously wrong here"); //$NON-NLS-1$
 } catch (IllegalAccessException e) {
                 // The API has changed, which seems amazingly unlikely.
 throw new Error ("Something is seriously wrong here"); //$NON-NLS-1$
 } catch (InvocationTargetException e) {
                 // The API has changed, which seems amazingly unlikely.
 throw new Error ("Something is seriously wrong here"); //$NON-NLS-1$
 }
         }

         return method;
     }

     /*
      * (non-Javadoc)
      *
      * @see org.eclipse.core.runtime.IExecutableExtension#setInitializationData(org.eclipse.core.runtime.IConfigurationElement,
      * java.lang.String, java.lang.Object)
      */
     public void setInitializationData(IConfigurationElement config,
             String propertyName, Object data) {
         // The data is really just a string (i.e., the method name).
 methodName = data.toString();
     }
 }

